Apparatus and method for producing epitaxial layers

Abstract

An apparatus and process for plasma enhanced chemical vapor deposition with an inductively coupled plasma with ion densities above 10 10 cm −3 and energies below 20 eV at the substrate enables epitaxial deposition of group IV and compound semiconductor layers at high rates and low substrate temperatures. The epitaxial reactor allows for in-situ plasma cleaning by chlorine and fluorine containing gaseous species.

1 . Reactor ( 100 ;  400 ;  500 ;  600 ) for low-energy plasma-enhanced chemical vapour deposition of an epitaxial semiconductor layer on a semiconductor substrate, comprising
 a metallic vacuum vessel ( 1 ) enclosing a vacuum chamber ( 2 ) connectable to a vacuum pump ( 18 ) for evacuating the vacuum chamber ( 2 ),   an enclosure ( 3 ), preferably a quartz or ceramic enclosure, contained inside said vacuum vessel ( 1 ), for defining a hot deposition region ( 4 ) inside the enclosure ( 3 ),   an enclosure ( 7 ), preferably a quartz or ceramic enclosure or an enclosure coated by a ceramic material or graphite, for defining a cold region ( 8 ) adjacent to said hot region ( 4 ) with a gate valve ( 10 ),   a vacuum pump ( 9 ) for pumping said hot deposition region ( 4 ) and said cold region ( 8 ),   gas insulation rings ( 12 ,  12 ′) to dynamically separate said hot deposition region ( 4 ) from said cold region ( 8 ) and said cold region ( 8 ) from said gate valve ( 10 ), to protect said gate valve ( 10 ) from corrosive gases and to lower the pressure gradient between said hot region ( 4 ) and said cold region ( 8 ),   a susceptor ( 5 ) carrying said substrate, said susceptor ( 5 ) being located inside said enclosure ( 3 ),   means ( 6 ) for indirectly heating said substrate,   sealed gas injection points ( 13 ,  15 ) in said enclosure ( 3 ) for feeding gases into said deposition region ( 4 ),   an inductively coupled radio-frequency (RF) plasma source comprising a coil ( 16 ) and/or a spiral antenna ( 17 ), both located outside the quartz enclosure ( 3 ),   
       wherein the power and frequency supplied to the coil ( 16 ) and/or the spiral antenna ( 17 ), and the pressure in said deposition region ( 4 ) are adjusted to provide
 ion energies below about 20 eV, preferably below 15 eV, or even more preferably below 10 eV 
 an ion density of at least 10 10  cm −3  at the substrate surface. 
 
     
     
         2 . The reactor ( 100 ) of  claim 1 , wherein said inductively coupled radio-frequency (RF) plasma source comprises said coil ( 16 ) and said spiral antenna ( 17 ). 
     
     
         3 . The reactor ( 600 ) of  claim 1 , wherein said enclosure ( 3 ) consists of two parts ( 3 ,  3 ′). 
     
     
         4 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , wherein said coil ( 16 ) or/and said spiral antenna ( 17 ) is/are each operated at a single frequency or at two different frequencies. 
     
     
         5 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , wherein said inductive coupled radio-frequency (RF) plasma source provides for a radio-frequency-plasma-assisted chemical vapor deposition inside said enclosure ( 3 ). 
     
     
         6 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , wherein said means ( 6 ) for indirectly heating said substrate are located outside said enclosure ( 3 ). 
     
     
         7 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , wherein low substrate temperature can be adjusted during epitaxial growth. 
     
     
         8 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , wherein said vacuum chamber ( 2 ) and hot deposition region ( 4 ) can be evacuated to a pressure below 10 −6  mbar, preferably even to pressures below 10 −8  mbar. 
     
     
         9 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , wherein a gas distribution ring ( 13 ) serves as gas inlet ( 11 ). 
     
     
         10 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 1 , further comprising an arrangement of coils outside the vessel ( 1 ) or enclosure ( 3 ) for shaping the plasma generated by said plasma source. 
     
     
         11 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 10 , wherein three flat coils ( 10 ,  20 ,  30 ), arranged in an off-centered configuration, serve as said arrangement of coils. 
     
     
         12 . The reactor ( 100 ;  400 ;  500 ;  600 ) of  claim 10 , wherein said arrangement of coils consists of two sets of three flat coils ( 10 ,  20 ,  30 ), arranged in a Helmholtz or Maxwell configuration. 
     
     
         13 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a SiC layer on a SiC substrate, whereby said substrate temperature is kept below 1200° C. 
     
     
         14 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a SiC layer on a Si substrate, whereby said substrate temperature is kept below 1000° C. 
     
     
         15 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a Si layer on a Si substrate, whereby said substrate temperature is kept below 800° C. and whereby ions with ion energies below 15 eV are employed. 
     
     
         16 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a Ge layer on a GaAs substrate, whereby said substrate temperature is kept below 500° C. 
     
     
         17 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a Ge layer on a GaAs substrate, whereby a Ge film is intentionally doped by diffusion from the substrate upon raising the substrate temperature to above 600° C. during or after growth. 
     
     
         18 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a Ge layer on a Si substrate, whereby said substrate temperature is kept at about 200-300° C. 
     
     
         19 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1  for growing a SiGe layer on a Si substrate, whereby said substrate temperature is chosen in accordance with the Ge content. 
     
     
         20 . Use of a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 19  for growing a SiGe layer on a Si substrate, whereby the substrate temperature is between 700 and 800° C. for a Ge content of 0 to 0.2, between 600 and 700° C. for a Ge content of 0.2 to 0.4, between 500 and 600° C. for a Ge content of 0.4 to 0.8 and below 500° C. for a Ge content of 0.8 to 1. 
     
     
         21 . Method for low-energy plasma-enhanced chemical vapour deposition of an epitaxial semiconductor layer on a semiconductor substrate, said method being carried out in a reactor ( 100 ;  400 ;  500 ;  600 ) according to  claim 1 , comprising the steps:
 loading ( 310 ) a wafer or substrate onto said susceptor ( 5 ),   heating ( 320 ) said wafer or substrate to a desired temperature,   performing ( 325 ) a low-energy plasma-enhanced chemical vapour deposition by feeding reactive gases into said deposition region ( 4 ) while ion energies below about 20 eV, preferably below 15 eV, and a density of at least 10 10  cm −3  at the substrate or wafer surface are provided.   
     
     
         22 . The method of  claim 21 , whereby another temperature is adjusted ( 320 ) before another a low-energy plasma-enhanced chemical vapour deposition is carried out. 
     
     
         23 . The method of  claim 21 , whereby a plasma wafer or substrate cleaning step is carried out prior to the low-energy plasma-enhanced chemical vapour deposition step. 
     
     
         24 . The method of  claim 21 , whereby an in-situ cleaning step of said deposition region ( 4 ) is carried out after said low-energy plasma-enhanced chemical vapour deposition step, by using chlorine or fluorine containing gases. 
     
     
         25 . The method of  claim 22 , whereby after said cleaning step said deposition region ( 4 ) is cleaned additionally with a pure hydrogen plasma. 
     
     
         26 . The method of  claim 21 , whereby, before the low-energy plasma-enhanced chemical vapour deposition, walls of the enclosure ( 3 ) are pre-coated, with the same material used in the low-energy plasma-enhanced chemical vapour deposition, in order to passivate O 2 , F and Cl impurities.